1. Field of the Invention
The present invention relates to an image forming apparatus, such as an ink jet printer, and more particularly, to a carriage for an ink cartridge of an ink jet printer having an improved latch system, which enables easy mounting and releasing of the ink cartridge.
2. Description of the Related Art
An ink jet printer ejects droplets of printing ink on a desired position to create a desired image on a paper. The printing ink is generally contained in an ink cartridge that is removably mounted in the ink jet printer. A structure of such a removable ink cartridge is disclosed in Japanese Publication No. 10-157162.
FIG. 1 is a cross sectional view showing a carriage for an ink cartridge of a conventional image forming apparatus, such as an ink jet printer, in which reference numerals 10, 13, 15, and 20 indicate a carriage, a guide rod, a snap hook, and a locking lever, respectively.
The carriage 10 is provided with a nozzle unit 12 in a carriage body 11, and the carriage 10 accommodates an ink cartridge 14 in connection with the nozzle unit 12. The carriage 10 reciprocally moves along the guide rod 13, and the ink cartridge 14 is secured in position as the snap hook 15 is hooked into the locking lever 20.
The carriage body 11 includes a shaft supporting portion 11a, on which the locking lever 20 is hinged, and an opening 11b, which allows the ink cartridge 14 to be removed from the carriage 10.
The locking lever 20 includes a rotary shaft 21, a cover plate 22, and a knob 23, and is secured to the carriage body 11 by the snap hook 15.
The rotary shaft 21 includes the shaft supporting portion 11a of the carriage body 11. The locking lever 20 pivots on the rotary shaft 21.
The cover plate 22 protects the ink cartridge 14 accommodated in the carriage body 11, and has protrusions 26 positioned on center portions of the cover plate 22. The protrusions 26 function to compress the ink cartridge 14 to lock the ink cartridge in the carriage 10.
The cover plate 22 is provided with a window 24 positioned thereon. The window 24 is sized to allow a pole type head 15b of the snap hook 15 to be inserted when the locking lever 20 is completely pivoted to a locking position.
The snap hook 15 includes a cantilever 15a and the pole type head 15b. 
The cantilever 15a deforms as the locking lever 20 moves to the locking position, and then snaps back to a non-stress state after the locking lever 20 reaches the locking position.
The pole type head 15b passes through the window 24, and is held by the knob 23, thereby locking the locking lever 20.
The knob 23 has a sliding slant 25 so that the pole-shaped head 15b of the snap hook 15 smoothly locks onto the knob 23.
In the carriage 10 constructed as above, to remove the ink cartridge 14, the cantilever 15a is first pushed in a direction “A”. Accordingly, the pole type head 15b is released through the window 24. The locking lever 20 is pivoted through a predetermined range by a recovering force of a pressure occurring when the protrusions 26 press the ink cartridge 14, to thus be released from the locking position. A user then opens the locking lever 20 to a full extent with her/his hands to replace the ink cartridge 14 with a new one.
But since such a locking device including the locking lever 20 mainly uses a resilient member such as the snap hook 15, a problem occurs if the resilient force is decreased or if the resilient member deforms due to repeated use. In this case, the ink cartridge 14 is not locked in the carriage 10 securely, and frequently unlocks as external shocks are applied.
Further, to remove the ink cartridge 14, a user is required to press the snap hook 15, manually pivot the locking lever 20, and then remove the ink cartridge 14 uprightly. Thus, the user experiences inconvenience, and an ink cartridge locking device that has an improved locking force and provides user convenience has been demanded.